Vehicle headlamp systems have been proposed that detect the presence of a forward vehicle (i.e., a vehicle positioned ahead of the reference vehicle). In one such system, a light source in of the forward vehicle, such as a tail lamp of a preceding vehicle or a headlamp of an oncoming vehicle is detected with an imaging sensor or the like. When no forward vehicle is detected, the state of projection of light from the headlamps of the reference vehicle is automatically changed from low beam to high beam. Thus, the driver's view of the road can be improved. (Refer to JP-A-2001-519744T and JP-7-108873A, for example.)
However, these systems suffer from certain disadvantages. When the reference vehicle turns to the left or right, a light source, such as a tail lamp of the preceding vehicle or a headlamp of an oncoming vehicle may move out of the range of detection of the imaging sensor or the like. As a result, the projection state of the headlamps is changed from low beam to high beam. Then, if the reference vehicle turns in the same direction toward the forward vehicle, switching back from high beam to low beam is carried out. As a result, the driver of the reference vehicle may be erroneously perceived to be flashing his/her lights by the driver of the forward vehicle. Furthermore, when the forward vehicle enters a curve or the reference vehicle is moving through a curve, the tail lamps of the forward vehicle enter within and move out of the range of detection of the imaging sensor or the like. For this reason, repeated switching from low beam to high beam and from high beam to low beam may occur. As a result, the driver of the reference vehicle may be erroneously perceived to be flashing his/her lights by the driver of the forward vehicle.